Tightening ring apparatus



FIG. 1 is a front elevational view of a tightening ring showing my new design;

FIG. 2 is a back elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a front elevational view thereof showing the ring in the operative state the broken lines are shown for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a tightening ring apparatus, as shown and described. 